Olefin polymerization catalyst

ABSTRACT

An improved olefin polymerization process employs an olefin polymerization catalyst produced from a polymerization procatalyst made from a magnesium alkoxide, a titanium tetraalkoxide, a tetravalent titanium halide, a phenolic compound and an alkanol. The procatalyst precursor is contacted with a tetravalent titanium halide and an electron donor to form the procatalyst which is subsequently converted to the olefin polymerization catalyst by contact with a cocatalyst and a selectively control agent.

This is a division of application Ser. No. 07/600,898 filed Oct. 22,1990 and now U.S. Pat. No. 5,077,357.

FIELD OF THE INVENTION

This invention relates to high activity olefin polymerization catalystsand to a method of polymerizing α-olefins which employs such catalysts.More particularly, the invention relates to a complex, solidmagnesium-containing, titanium-containing precursor of an olefinpolymerization catalyst component and to the component and the catalystproduced therefrom.

BACKGROUND OF THE INVENTION

The production of polymers or copolymers of lower α-olefins,particularly ethylene and propylene, has gained substantial commercialacceptance. The polymeric products are inexpensive and exhibit a numberof commercially useful properties. In the case of the polymerization ofethylene, the process is relatively uncomplicated in that the producttype is not influenced by the manner in which the ethylene molecules addto the growing polymer chain and the polymeric product does not exist instereoisomeric forms.

In the case of the polymerization of propylene, however, the presence ofpendant methyl groups on the polymeric chain provides the possibility ofseveral types of product depending upon the steric regularity with whichthe propylene units add to the growing polymer chain. Much, if not most,of the commercial polypropylene is crystalline and results from thestereoregular addition of propylene units in a regular head-to-tailmanner. The polypropylene in which the addition of units is random istermed atactic. This amorphous form is generally less desirable and, ifpresent in significant quantities, must be removed as by extraction inorder to obtain a more desirable crystalline product.

Also significant from a commercial standpoint is the activity of thepolymerization catalyst. A number of the early polymerization catalysts,e.g., trivalent titanium, chromium or vanadium catalysts, were ofrelatively low activity and the polyolefin product contained asignificant proportion of catalyst residues. The removal of suchresidues as by a deashing step was required in order to obtaincommercially acceptable properties. The more recent olefinpolymerization catalysts are stereoregular and of sufficient activity sothat extraction and/or deashing steps are not required.

In the terms now conventionally employed for the components, the highactivity olefin polymerization catalysts are formed from a procatalystwhich typically contains magnesium, titanium and halide moieties as wellas an electron donor, a cocatalyst which is usually an organoaluminumcompound and a selectivity control agent which may be provided as apartial or total complex with the cocatalyst. Although each of thecomponents has a considerable influence on the polymerization catalystand process and the polymer product thereby produced, the nature of thecatalyst as well as the polymerization product seems to be mostinfluenced by the procatalyst. Much of the research directed towardimprovement of the olefin polymerization process has been directedtoward improvement of the procatalyst component.

Kioka et al, U.S. Pat. No. 4,300,649, describe a solid catalystcomponent (procatalyst) obtained by heating a soluble magnesium compoundsuch as magnesium chloride with a higher alcohol in the presence of anester to produce a solution which is added to titanium tetrachloride andan electron donor to form the procatalyst. Band, U.S. Pat. No.4,472,521, reacts a magnesium alkoxide with a titanium alkoxide whereineach alkoxide has 4 or more carbon atoms in the presence of aromatichydrocarbon. Titanium tetrachloride and an electron donor are added tothe resulting solution to form a procatalyst which is post-treated withtransition metal halide. Arzoumanidis et al, U.S. Pat. No. 4,540,679,produce a catalyst component by contacting a suspension of magnesiumethoxide in ethanol with carbon dioxide. The addition of anorganoaluminum compound in hydrocarbon solvent to the resulting solutionproduces spherical particles which are used as a support for titaniummoieties upon contacting the particles with titanium tetrachloride.Nestlerode et al, U.S. Pat. No. 4,728,705, solubilize magnesium ethoxidein ethanol with carbon dioxide and spray dry the resulting solution oralternatively use the solution to impregnate catalyst support particles.The particles resulting from either modification are useful in theproduction of a procatalyst of desirable morphology.

A somewhat different type of catalyst component precursor is describedby Job, U.S. Pat. No. 4,710,428, wherein a crystalline magnesiumcompound of the general formula

    Mg.sub.4 (OR).sub.6 (ROH).sub.10 A                         (I)

is formed in which R independently is lower alkyl of up to 4 carbonatoms inclusive and A is one or more anions having a total oxidationstate of -2. This complex magnesium compound is contacted with atetravalent titanium halide and an electron donor to form an olefinpolymerization procatalyst. The use of such insoluble magnesiumcompounds has certain advantages in that the olefin polymerizationcatalysts produced from such complexes by way of the intermediateprocatalyst are good high activity polymerization catalysts,particularly for the polymerization or copolymerization of propylene andproduce polymer of predetermined morphology. It would be of advantage,however, to provide improved olefin polymerization catalysts.

SUMMARY OF THE INVENTION

The present invention provides solid, magnesium-containing,titanium-containing olefin polymerization procatalyst precursor and theprocatalyst and olefin polymerization catalyst produced therefrom. Thepresent invention also provides the improved process of polymerizinglower α-olefins which employs such catalyst. The catalyst of theinvention is a high activity olefin polymerization catalyst and its useresults in production of polyolefin product of good properties in animproved yield.

DESCRIPTION OF THE INVENTION

The present invention contemplates the production of a complex, solidolefin polymerization procatalyst precursor containing moieties ofmagnesium and titanium and probably moieties of at least some of halide,alkoxide and a phenolic compound. Such complex procatalyst precursorsare produced by contacting a magnesium alkoxide, a titanium alkoxide, atitanium halide, a phenolic compound and an alkanol. Removal of alkanolfrom the resulting solution provides the solid procatalyst precursor asopaque, spheroidal particles. The procatalyst precursor is contactedwith a tetravalent titanium halide, a halohydrocarbon and an electrondonor to form the procatalyst which in turn is contacted with anorganoalumnum cocatalyst and a selectivity control agent to form theolefin polymerization catalyst.

The solid olefin polymerization procatalyst precursor is a complex ofindefinite stoichiometry formed from a magnesium alkoxide, a tetravalenttitanium alkoxide, a titanium tetrahalide, a phenolic compound and analkanol. The alkoxide moieties in these reactants independently have upto 4 carbon atoms inclusive. The alkoxide moieties within one reactantare the same or different if more than one alkoxide moiety is present,and the alkoxide moieties of one reactant are the same as or differentfrom alkoxide moieties in other reactants. Although alkoxide moietiessuch as methoxide, propoxide, isopropoxide and butoxide are useful, thepreferred alkoxide moieties are ethoxide. The halide moieties of thetitanium tetrahalide are preferably chloride or bromide with chloridebeing particularly preferred.

The phenolic compound used in the production of the procatalystprecursor is selected from phenol or activating group-substitutedphenol. By the term "activating group" is meant an aromatic ring carbonatom substituent free from active hydrogens which is ortho-paradirecting for conventional aromatic ring substitution and which isgenerally but not invariably electron donating. Illustrative of suchgroups are alkyl of up to 5 carbon atoms inclusive, e.g., methyl, ethyl,isopropyl or n-butyl; alkoxy of up to 5 carbon atoms, e.g., methoxy,ethoxy or i-propoxy; halo, particularly chloro or bromo; anddialkylamino wherein each alkyl independently has up to 5 carbon atomsinclusive such as dimethylamino, diethylamino and methylpropylamino.Illustrative of phenolic compounds which are useful in the production ofthe procatalyst precursor are phenol, o-cresol, p-cresol,3-methoxyphenol, 4-dimethylaminophenol, 2,6-di-tert-butyl-4-methylphenoland p-chlorophenol. Of such phenolic compounds the use ofalkyl-substituted phenol is preferred and particularly preferred is theuse of o-cresol.

The complex, solid procatalyst precursor is produced by contacting thereactants in an inert reaction diluent. The diluent is suitably ahydrocarbon diluent such as isopentane, isooctane, cyclohexane ortoluene or a halohydrocarbon such as methylene chloride orchlorobenzene. Isooctane is a preferred hydrocarbon diluent andchlorobenzene is a preferred halohydrocarbon diluent. As stated, theformation of the procatalyst precursor does not appear to observeconventional molar stoichiometry. However, the production of theprecursor is illustrated by the following partial general equation whichemploys the preferred alkoxide and halide moieties,

    3 Mg(OEt).sub.2 +x Ti(OEt).sub.4 +y TiCl.sub.4 +z o-cresol+n EtOH→

wherein y is more than about 0.1 but less than about 0.8, preferablymore than 0.3 but less than 0.5, (x+y) is more than about 0.2 but lessthan about 3, preferably more than about 0.5 but less than about 2, z ismore than about 0.05 but less than about 3, preferably more than about0.1 but less than about 2, and n is more than about 0.5 but less thanabout 9, preferably more than about 2 but less than about 5.

The initial interaction of the reactants in the reaction diluent takesplace in a non-gaseous state at a moderate reaction temperature.Suitable reaction temperatures are from about 30° C. to about 120° C.,preferably from about 35° C. to about 90° C. This initial heatingresults in the formation of a generally clear solution. This solution isthen heated to a higher temperature to remove alkanol, ethanol in thepreferred modification, typically as an azeotrope with a portion of theinert diluent. The temperature of this second heating will depend inpart on the boiling point of any azeotrope containing alkanol which isformed. Typical heating (azeotroping) temperatures are from about 70° C.to about 120° C., preferably from about 85° C. to about 110° C. Theremoval of the alkanol results in the formation of the procatalystprecursor in the form of solid, opaque, spheroidal particles.

The olefin polymerization procatalyst precursor is converted to theprocatalyst by reaction with a tetravalent titanium halide, an optionalhalohydrocarbon and an electron donor. The tetravalent titanium halideis suitably an aryloxy- or alkoxy di- or trihalide such asdiethoxytitanium dichloride, dihexyloxytitanium dibromide ordiisopropoxytitanium chloride or the tetravalent titanium halide is atitanium tetrahalide such as titanium tetrachloride or titaniumtetrabromide. A titanium tetrahalide is preferred as the tetravalenttitanium halide and particularly preferred is titanium tetrachloride.

The optional halohydrocarbon employed in the production of olefinpolymerization procatalyst is a halohydrocarbon of up to 12 carbon atomsinclusive, preferably up to 9 carbon atoms inclusive, which contains atleast one halogen atom and in the case of aliphatic halohydrocarbonscontains at least two halogen atoms. Exemplary aliphatichalohydrocarbons include methylene chloride, methylene bromide,chloroform, carbon tetrachloride, 1,2-dibromoethane,1,1,2-trichloroethane, trichlorocyclohexane, dichlorofluoromethane andtetrachlorooctane. Aromatic halohydrocarbons which are suitably employedare chlorobenzene, bromobenzene, dichlorobenzene and chlorotoluene. Ofthe aliphatic halohydrocarbons, carbon tetrachloride and1,1,2-trichloroethane are preferred but particularly preferred is thearomatic halohydrocarbon chlorobenzene.

The electron donors which are suitably utilized in procatalystproduction are those electron donors free from active hydrogens whichare conventionally employed in the formation of titanium-basedprocatalysts. Such electron donors include ethers, esters, amines,imines, nitriles, phosphines, stibines, and arsines. The preferredelectron donors are esters, particularly alkyl esters of aromaticmonocarboxylic or dicarboxylic acids. Examples of such electron donorsare methyl benzoate, ethyl benzoate, ethyl p-ethoxybenzoate, ethylp-methylbenzoate, diethyl phthalate, dimethyl naphthalene dicarboxylate,diisobutyl phthalate and diisopropyl terephthalate. The electron donoris a single compound or is a mixture of compounds but preferably theelectron donor is a single compound. Of the preferred ester electrondonors, ethyl benzoate and diisobutyl phthalate are particularlypreferred.

The precise manner in which the procatalyst precursor, thehalohydrocarbon and the electron donor are contacted is material but notcritical. In one embodiment, the tetravalent titanium halide is added toa mixture of the electron donor and solid procatalyst precursor. Bestresults are obtained, however, if the electron donor is mixed with thetetravalent titanium halide and halohydrocarbon and the resultingmixture is used to contact the solid procatalyst precursor. Otherprocedures are also suitable but less preferred. The solid product whichresults is typically washed at least once with the tetravalent titaniumhalide and the halohydrocarbon, taken together or employed separately.It is often useful to include an acid chloride, e.g., benzoyl chlorideor phthaloyl chloride in at least one wash to further facilitate thereplacement of at least a portion of the alkoxide moieties in theprocatalyst precursors with halide moieties. This replacement, oftentermed a halogenation, is well known in the art. The solid olefinpolymerization procatalyst which results is then typically washed with alight hydrocarbon such as isooctane to remove soluble titaniumcompounds.

In the preferred modification the mixture of procatalyst precursor,tetravalent titanium halide, electron donor and halohydrocarbon ismaintained at an elevated temperature, for example, a temperature of upto about 150° C. Best results are obtained if the materials arecontacted initially at or about ambient temperature and then heated.Sufficient tetravalent titanium halide is provided to convert at least aportion and preferably at least a substantial portion of the alkoxidemoieties of the procatalyst precursor to halide groups. This replacementis conducted in one or more contacting operations, each of which isconducted over a period of time ranging from a few minutes to a fewhours and it is preferred to have halohydrocarbon present during eachcontacting. Sufficient electron donor is provided so that the molarratio of electron donor to the magnesium present in the solidprocatalyst is from about 0.01:1 to about 1:1, preferably from about0.05:1 to about 0.5:1. The final washing with light hydrocarbon producesa procatalyst which is solid and granular and when dried is storagestable provided that oxygen and active hydrogen compounds are excluded.Alternatively, the procatalyst is used as obtained from the hydrocarbonwashing without the need of drying. The procatalyst thus produced isemployed in the production of an olefin polymerization catalyst bycontacting the procatalyst with a cocatalyst and a selectivity controlagent.

The cocatalyst component of the olefin polymerization catalyst is anorganoaluminum compound selected from the cocatalysts conventionallyemployed with titanium-based procatalysts. Illustrative organoaluminumcocatalysts include trialkylaluminum compounds, alkylaluminum alkoxidecompounds and alkylaluminum halide compounds in which each alkylindependently has from 2 to 6 carbon atoms inclusive. The preferredorganoaluminum cocatalysts are halide free and particularly preferredare the trialkylaluminum compounds such as triethylaluminum,triisopropylaluminum, triisobutylaluminum and diethylhexylaluminum.Triethylaluminum is a preferred trialkylaluminum cocatalyst. Theorganoaluminum cocatalyst, during formation of the olefin polymerizationcatalyst, is employed in a molar ratio of aluminum to titanium of theprocatalyst of from about 1:1 to about 150:1, but preferably in a molarratio of from about 10:1 to about 100:1.

The selectivity control agents which are used in the production ofolefin polymerization catalyst are those selectivity control agentsconventionally employed in conjunction with titanium-based procatalystsand organoaluminum cocatalysts. Illustrative of suitable selectivitycontrol agents are those classes of electron donors employed inprocatalyst production as described above as well as organosilanecompounds including alkylalkoxysilanes and arylalkoxysilanes of theformula

    R'.sub.r Si(OR).sub.4-r                                    (II)

wherein R' independently is aryl or alkyl of up to 10 carbon atomsinclusive, R independently is alkyl of up to 4 carbon atoms inclusiveand r is 1 or 2. The preferred selectivity control agents are esters ofaromatic monocarboxylic or dicarboxylic acids, particularly alkylesters, such as ethyl p-ethoxybenzoate, diisobutyl phthalate, and ethylp-methylbenzoate, or the preferred selectivity control agents arealkylalkoxysilanes such as ethyldiethoxysilane,diisobutyldimethoxysilane, cyclohexylmethyldimethoxysilane orpropyltrimethoxysilane. In one modification, the selectivity controlagent is a portion of the electron donor added during the procatalystproduction. In an alternate modification the selectivity control agentis provided at the time of the contacting of procatalyst and cocatalyst.In either modification the selectivity control agent is provided in aquantity of from about 0.1 mole to about 100 moles per mol of titaniumin the procatalyst. Preferred quantities of selectivity control agentare from about 0.5 mole to about 25 mole per mole of titanium in theprocatalyst.

The olefin polymerization catalyst is produced by known procedures ofcontacting the procatalyst, the cocatalyst and the selectivity controlagent. The method of contacting is not critical. In one modification thecatalyst components are simply mixed in a suitable reactor and thepreformed catalyst thereby produced is introduced into thepolymerization reactor when initiation of polymerization is desired. Inan alternate modification, the catalyst components are introduced intothe polymerization reactor where the catalyst is formed in situ.

The olefin polymerization catalyst formed from the complex solidprocatalyst precursor by way of the procatalyst is useful in thepolymerization under polymerization conditions of lower α-olefins andparticularly in the polymerization of straight chain α-olefins of up to4 carbon atoms, i.e., ethylene, propylene and 1-butene, or mixturesthereof. The precise procedures and conditions of the polymerization arebroadly conventional but the olefin polymerization process, by virtue ofthe use therein of the polymerization catalyst formed from the solidcomplex procatalyst precursor, provides polyolefin product andparticularly polypropylene product having a relatively high bulk densityin quantities which reflect the relatively high productivity of theolefin polymerization catalyst. The polymerization product is suitably ahomopolymer such as polyethylene or polypropylene, particularlypolypropylene, as when a single α-olefin monomer is supplied to thepolymerization process. Alternatively, the catalyst and process of theinvention are useful in the production of copolymers includingcopolymers of ethylene and propylene such as EPR and polypropyleneimpact copolymer as when two or even more α-olefin monomers are suppliedto the polymerization process.

Polymerization is suitably conducted under polymerization conditions ina gas-phase process employing one or more fluidized beds of catalyst oris conducted as a slurry-phase process employing as diluent an inertmaterial such as propane or a liquified monomer of the polymerizationsuch as propylene. The molecular weight of the product is customarilyinfluenced by the provision of molecular hydrogen as is known in theart. The polymerization is conducted in a batchwise manner or in acontinuous or semi-continuous manner with constant or intermittentaddition of catalyst or catalyst components to the polymerizationreactor.

In general, the productivity of an olefin polymerization catalystexhibits an inverse relationship with selectivity so that many highlyactive polymerization catalysts have a good productivity but arelatively low stereospecificity. The catalysts of the invention exhibitgood productivity while retaining desirably high stereospecificity sothat the polymeric product obtained through the use of such a catalysthas good properties without the necessity of an extraction or deashingstep.

The invention is further illustrated by the following IllustrativeEmbodiments which should not be regarded as limiting.

ILLUSTRATIVE EMBODIMENT I

In an 8-ounce bottle, 2.0 g (10.5 mmol) of titanium tetrachloride, 3.76g (15.7 mmol) of 95% titanium tetraethoxide, 8.12 g (71 mmol) ofmagnesium ethoxide and 0.94 g (8.7 mmol) of o-cresol were slurried in100 g of chlorobenzene and 5.4 g of ethanol was added while the mixturewas stirred at 440 rpm. The bottle was capped and immersed in an oilbath at 105° C. Within a few minutes, the magnesium ethoxide haddissolved but the solution remained murky. After about 1 hour, the capwas removed and the mixture was stirred for 2 additional hours andfiltered while hot. The solids thus recovered were washed once with warmchlorobenzene, once with isooctane and dried under flowing nitrogen. Thesolids, 9.2 g, were nearly white, opaque spheroids.

ILLUSTRATIVE EMBODIMENT II

In a 2-liter flask equipped with a teflon stir paddle were slurried 39.6g (165 mmol) of 95% titanium tetraethoxide, 81.2 g (710 mmol) ofmagnesium ethoxide, 9.4 g (86.7 mmol) of o-cresol, 52.5 g (1.14 mole) ofethanol and 800 g of chlorobenzene. While the mixture was stirred atabout 300 rpm under a nitrogen blanket, a solution of 18 g (95 mmol) oftitanium tetrachloride in 200 g of chlorobenzene was rapidly added. Theflask was heated to 60°-65° C. and a nearly complete dissolution of allsolids was obtained after about 2 hours. The temperature of the flaskwas then raised to 92° C. and a gentle stream of nitrogen was passedover the surface of the flask contents and the evolved ethanol wascollected in a nitrogen bubber. After stirring overnight, the volume haddecreased by about 5% and a murky solution was obtained. The slurry wasfiltered while warm and the solids thus recovered were washed once withchlorobenzene, twice with isooctane and dried under flowing nitrogen. Ayield of 110.4 g of particles in the 15-70 micron size range wasobtained. The particles were primarily opaque spheroids. The elementalanalysis of the particles was 13.6% by weight magnesium and 8.1% byweight titanium.

ILLUSTRATIVE EMBODIMENT III

The olefin polymerization procatalyst precursors of each of IllustrativeEmbodiments I and II were converted to procatalysts by digesting for 60minutes at 110° C. sufficient precursor to provide 30-50 mmol ofmagnesium in 150 ml of a 50/50 mixture by volume of chlorobenzene andtitanium tetrachloride containing sufficient diisobutyl phthalate toprovide a concentration of about 40 mmol/liter. This digest was followedby a first wash for 60 minutes at 110° C. with 150 ml of a fresh 50/50mixture containing 6 mmol/liter of phthaloyl chloride. A second wash for30 minutes at 110° C. with fresh 50/50 mixture then followed. Theresulting solid was washed once with isooctane at 90° C. and twice withisooctane at room temperature and then dried with nitrogen at 50° C. Theprocatalyst obtained from the precursor of Illustrative Embodiment I wasfound to contain 2.4% by weight titanium, 18.7% by weight magnesium and60.0% by weight chlorine. The procatalyst obtained from the precursor ofIllustrative Embodiment II was found to contain 2.89% by weighttitanium, 19.4% by weight magnesium and 59.8% by weight chlorine.

ILLUSTRATIVE EMBODIMENT IV

The procatalysts of Illustrative Embodiment IV were converted to olefinpolymerization catalysts by mixing with triethylaluminum cocatalyst anddiisobutyldimethoxysilane selectivity control agent. The quantities ofcatalyst components were such that the aluminum/silicon/titanium ratiowas 70/20/1. The components were mixed prior to injection into a 1-literautoclave containing propylene and the resulting slurry-phasepolymerization employing liquid propylene as diluent took place at 67°C. for 1 hour. Molecular hydrogen, 43 mmol, was also added to theautoclave. The results of the polymerizations are given in the Tablewhere the origin of the procatalyst precursor is indicated. Also shownby the terms H and R, respectively, are the situations where thecatalyst was injected into the autoclave with contents already heated to67° C. (H) and the case where the catalyst was injected into theautoclave at room temperature and the mixture was heated to 67° C. overabout 15 minutes (R). The productivity of the catalyst is measured interms of the kg of polymer obtained per g of procatalyst per hour. Thestereospecificity of the catalyst is evaluated in terms of the xylenesolubles content (termed XS) as measured in accordance with theregulations of the U.S. Food and Drug Administration. The test forxylene solubles is conducted by dissolving the polymer in xylene underreflux. The flask containing the dissolved polymer is then immersed in awater bath at 25° C. for 1 hour without stirring while the xyleneinsoluble portion precipitates. The precipitate is recovered byfiltration and the solubles content is determined by evaporating analiquot of the filtrate and drying and weighing the residue. The xylenecontent consists primarily of amorphous (atactic) polymer and lowmolecular weight crystalline polymer. Also in the Table the bulk density(BD) of the polymer is indicated in terms of g of polymer per cc. Ineach case the polymer consisted of essentially spheroidal particles.

                  TABLE                                                           ______________________________________                                        Illustrative                                                                  Embodiment         Productivity,                                                                              XS,   BD                                      Precursor Injection                                                                              kg/g cat hr  % wt  g/cc                                    ______________________________________                                        1         H        35.4         3.3   0.390                                             R        36.6         3.2   0.447                                   2         H        33.1         3.5   0.413                                             R        50.0         3.2   0.471                                   ______________________________________                                    

What is claimed is:
 1. A complex solid olefin polymerization procatalystprecursor obtained by heating a reaction mixture consisting essentiallyof a magnesium alkoxide, wherein the alkoxide moieties independentlyhave up to four carbon atoms inclusive, a titanium alkoxide, wherein thealkoxide moieties independently have up to four carbon atoms inclusive,a titanium halide, a phenolic compound selected from phenol or phenolsubstituted with a group free from active hydrogen atoms which isortho-para directing for aromatic ring substitution and an alkanol, andremoving alkanol from the resulting mixture.
 2. The procatalystprecursor of claim 1 wherein the phenolic compound is selected fromphenol or substituted by alkyl, alkoxy, halo or dialkylamino.
 3. Theprocatalyst precursor of claim 2 wherein the titanium halide is titaniumchloride.
 4. The procatalyst precursor of claim 3 wherein the magnesiumalkoxide is magnesium ethoxide, the titanium alkoxide is titaniumtetraethoxide and the alkanol is ethanol.
 5. The procatalyst precursorof claim 4 wherein the molar stoichiometry of the contacting is 3magnesium ethoxide, x titanium tetraethoxide, y titanium tetrachloride,z phenolic compound and n ethanol, wherein y is more than about 0.3 butless than about 0.5, (x+y) is more than about 0.5 but less than about 2,z is more than about 0.1 but less than about 2, and n is more than about2 but less than about
 5. 6. The solid olefin polymerization procatalystproduced by contacting the complex, solid procatalyst precursor of claim1 with a tetravalent titanium halide, a halohydrocarbon and an electrondonor.
 7. The procatalyst of claim 6 wherein the tetravalent titaniumhalide is titanium tetrahalide.
 8. The procatalyst of claim 1 whereinthe phenolic compound is selected from phenol or phenol substituted byalkyl, alkoxy, halo or dialkylamino.
 9. The procatalyst of claim 8wherein the electron donor is alkyl ester of aromatic monocarboxylic ordicarboxylic acid.
 10. The procatalyst of claim 9 wherein the magnesiumalkoxide is magnesium ethoxide, the titanium alkoxide is titaniumtetraethoxide and the alkanol is ethanol.
 11. The procatalyst of claim10 wherein titanium tetrahalide is titanium tetrachloride.
 12. Theprocatalyst of claim 11 wherein the ester is ethyl benzoate.
 13. Theprocatalyst of claim 11 wherein the ester is diisobutyl phthalate. 14.The olefin polymerization catalyst obtained by contacting theprocatalyst of claim 6 with an organoaluminum cocatalyst andd aselectivity control agent.
 15. The catalyst of claim 14 wherein theorganoaluminum cocatalyst is trialkylaluminum.
 16. The catalyst of claim15 wherein the selectivity control agent is an alkyl ester of anaromatic monocarboxylic or dicarboxylic acid or an organosilane compoundof the formula

    R'.sub.r Si(OR).sub.4-r

wherein R' independently is alkyl or aryl of up to 10 carbon atomsinclusive, R independently is alkyl of up to 4 carbon atoms and r is 1or
 2. 17. The catalyst of claim 16 wherein the selectivity control agentis an ester.
 18. The catalyst of claim 17 wherein the trialkylaluminumis triethylaluminum.
 19. The catalyst of claim 18 wherein the ester isethyl p-ethoxybenzoate.
 20. The catalyst of claim 18 wherein the esteris diiisobutyl phthalate.
 21. The catalyst of claim 16 wherein theselectivity control agent is an organosilane.
 22. The catalyst of claim21 wherein the trialkylaluminum is triethylaluminum.
 23. The catalyst ofclaim 22 wherein the organosilane is diisobutyldimethoxysilane.
 24. Thecatalyst of claim 22 wherein the organosilane is propyltrimethoxysilane.25. The catalyst of claim 22 wherein the organosilane iscyclohexyldimethoxysilane.